Far-off planetary worlds may sustain life

Life could exist in the atmospheres of brown dwarfs and gas giants, research suggests.

A study from the Centre for Exoplanet Science shows the potential for habitable environments in the atmospheres of brown dwarfs and planets with inhospitable lower atmospheres or surfaces, using a theoretical model of an organism.

Our study of hypothetical small, simple life forms on a cool brown dwarf – an object larger than a planet and smaller than a star – suggests that they could adapt to survive in such habitats. The organisms could evolve to cope in the gravity, temperature and wind conditions in such environments, where water and nutrients may also be found.

We suggest that such life forms could survive on planets whose surface or lower atmosphere is too hot, cold, dry or dense to support life. In addition, some cool brown dwarfs are free-floating - that is, they don't orbit a star - which challenges the traditional view of habitability of a terrestrial planet orbiting a Sun-like star. In light of the finding, scientists may have previously underestimated how much of the universe is potentially habitable.

This would include the possibility of habitable atmospheres in gas giants like Jupiter, Saturn, Uranus and Neptune. Beyond our solar system, billions of such worlds at the distant reaches of our galaxy may have such habitable zones. The closest of these atmospheric habitable zones could be less than 30 light years away, which may be within the reach of powerful astronomy telescopes likely to be developed in the next decade. This would enable scientists to search for signs of life in distant worlds.

However, although these calculations show the potential for habitable conditions, they say nothing about whether or not these bodies are actually inhabited, or how life could arise in an atmosphere.

The study was the first to be published by the Centre for Exoplanet Science. It appears some 40 years after some of the ideas behind the study were published in the same journal by pioneering scientist Carl Sagan.

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